A structure is deposited as an artificial fish reef in the sea to forman artificial seaweed bed. The structure is made of steel, stone or wood. The artificial seaweed bed is formed in a space formed of the structure. The space provides a habitat for a seaweed or a plant plankton. The process for the formation of the artificial seaweed is widely applicable.
The conventional seaweed bed attracts grown fishes. Accordingly, the seaweed bed provides an artificial fishing ground. However, the amount of the seaweed planted on the artificial bed has remarkably been decreased within several years from the time of depositing the artificial fish reef. Therefore, the conventional artificial seaweed bed cannot provide a nursery ground for a fish. In other words, the seaweed bed cannot protect fish eggs and young fishes of a plankton life type. A seaweed or a plant plankton should be planted on an artificial fish reef for a long term to provide a nursery ground for fishes. It is now required to develop such an artificial seaweed bed and an artificial fish reef.
By the way, Katsuhiko Matsunaga (Hokkaido University) describes that minerals dissolved in seawater such as iron, manganese, silicon and phosphorus are necessary for cultivating a seaweed or a plant plankton on a seaweed bed (Dairy Politics and Economics News, Jan. 1, 1988). He further reports that the cultivating effect can be remarkably increased by dissolving a ferrous ion (divalent iron ion) in seawater.
Further, it has been experimentally known that a sunken ship is thickly grown with seaweed, which attracts many fishes. The ship in the sea forms an artificial fish reef made of iron. It is assumed that a part of iron of the ship is dissolved in seawater as a ferrous ion, which can be directly furnished to the organisms on the seaweed bed. The assumption is supported by data about iron contents in seaweed. The iron content in a seaweed planted on the artificial iron reef is twice or more the content in a seaweed planted on a natural rock reef.